Open pattern inductor

ABSTRACT

Various embodiments includes a stacked open pattern inductor fabricated above a semiconductor substrate. The stacked open pattern inductor includes a plurality of parallel open conducting patterns embedded in a magnetic oxide or in an insulator and a magnetic material. Embedding the stacked open pattern inductor in a magnetic oxide or in an insulator and a magnetic material increases the inductance of the inductor and allows the magnetic flux to be confined to the area of the inductor. A layer of magnetic material may be located above the inductor and below the inductor to confine electronic noise generated in the stacked open pattern inductor to the area occupied by the inductor. The stacked open pattern inductor may be fabricated using conventional integrated circuit manufacturing processes, and the inductor may be used in connection with computer systems.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/722,094 filed Nov. 25, 2003 now U.S. Pat. No. 7,380,328, which is adivisional of U.S. application Ser. No. 10/280,180 filed Oct. 25, 2002,now issued as U.S. Pat. No. 6,653,196, which is a divisional of U.S.application Ser. No. 09/261,595 filed on Feb. 26, 1999, now issued asU.S. Pat. No. 6,566,731, the specification of these applications areincorporated herein by reference.

FIELD

The present invention relates to inductors, and more particularly, toinductors used in integrated circuits.

BACKGROUND

The telecommunications and computer industries are driving the demandfor miniaturized analog and mixed signal circuits. Inductors are acritical component in the traditional discrete element circuits, such asimpedance matching circuits, resonant tank circuits, linear filters, andpower circuits, used in these industries. Since traditional inductorsare bulky components, successful integration of the traditional discreteelement circuits requires the development of miniaturized inductors.

One approach to miniaturizing an inductor is to use standard integratedcircuit building blocks, such as resistors, capacitors, and activecircuitry, such as operational amplifiers, to design an active inductorthat simulates the electrical properties of a discrete inductor. Activeinductors can be designed to have a high inductance and a high Q factor,but inductors fabricated using these designs consume a great deal ofpower and generate noise.

A second approach to miniaturizing an inductor is to fabricate asolenoid type inductor with a core using conventional integrated circuitmanufacturing process technology. Unfortunately, conventional integratedcircuit process steps do not lend themselves to precisely andinexpensively fabricating a helical structure with a core. So,integrated circuit process technology is only marginally compatible withmanufacturing a solenoid type inductor.

A third approach, sometimes used in the fabrication of miniatureinductors in gallium arsenide circuits, is to fabricate a spiral typeinductor using conventional integrated circuit processes. Unfortunately,this approach has a high cost factor associated with it when applied tofabricating inductors for use in silicon integrated circuits. Siliconintegrated circuits operate at lower frequencies than gallium arsenidecircuits, and generally require inductors having a higher inductancethan inductors used in gallium arsenide circuits. The higher inductanceis realized in a spiral inductor occupying a large surface area on thesilicon substrate.

For these and other reasons there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a stacked open pattern inductor.

FIG. 1B is a top view of the lower open conductive pattern of thestacked open pattern inductor of FIG. 1A.

FIG. 1C is a top view of the middle open conductive pattern of thestacked open pattern inductor of FIG. 1A.

FIG. 1D is a top view of the upper open conductive pattern of thestacked open pattern inductor of FIG. 1A.

FIG. 2A is a side view of a slice of the stacked open pattern inductorof FIG. 1A taken between the lines X and Y and encapsulated in amagnetic oxide.

FIG. 2B is a section of FIG. 1A showing the lower encapsulated openinductor pattern of FIG. 1A.

FIG. 2C is a section of FIG. 1A showing the a contact site exposing thelower open inductor pattern.

FIG. 2D is a section of FIG. 1A showing the contact site filled with aconductive material.

FIG. 3A is a side view of a slice of FIG. 1A taken between lines X and Yshowing the lower open inductor pattern embedded in an insulator and amagnetic material.

FIG. 3B is a side view of a slice of FIG. 1A taken between lines X and Yshowing the open inductor embedded in insulating layers and magneticmaterial layers.

FIG. 4 is an exploded perspective view of a stacked open inductorshowing magnetic field lines.

FIG. 5 is a block diagram of a computer system suitable for use inconnection with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and thatstructural, logical and electrical changes may be made without departingfrom the spirit and scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present invention is defined by the appendedclaims.

Inductors intended for use in circuits fabricated on a silicon substrateusually operate at lower frequencies and require larger inductances thaninductors intended for use in circuits fabricated on a gallium arsenidesubstrate. As mentioned above, a larger inductance is usually realizedin silicon by having the inductor occupy a larger surface area.According to one embodiment of the present invention, rather thanincreasing the inductance by increasing the surface area occupied by theinductor, a larger inductance is achieved by encapsulating an inductorin a magnetic material.

Referring to FIG. 1A, a perspective view of the conductive elements ofone embodiment of open pattern stacked inductor 100 is shown. Openpattern stacked inductor 100 is made up of three vertically stacked openconductive patterns 103, 106, and 109 coupled together by conductivesegments 112 and 115. Open conductive patterns 103, 106, and 109 eachhave an outside edge 113, 116, and 117, respectively.

FIGS. 1B, 1C, and 1D show a top view of each open conductive pattern ofFIG. 1A. FIG. 1B shows a top view of open conductive pattern 103. FIG.1C shows a top view of open conductive pattern 106. FIG. 1D shows a topview of open conductive pattern 109.

In the embodiment shown in FIG. 1A, each of the three open conductivepatterns is an open rectangle. However, the present invention is notlimited to a particular open pattern shape. Any shape or shapes that canbe combined to form a device in which the voltage across the device isproportional to the derivative of the current passing through the deviceis suitable for use in connection with the present invention.

Referring to FIG. 1B, open conductive pattern 103 is fabricated from aconductive material. In one embodiment, open conductive pattern 103 isfabricated from copper. In alternate embodiments, open conductor 103 isfabricated from gold, aluminum, silver, or an alloy of copper, gold,aluminum or silver. However, the fabrication of open conductive pattern103 is not limited to a particular material. Any material that iscapable of conducting current is suitable for use in connection with thepresent invention.

Open conductive pattern 103 has a cross-sectional area. As thecross-sectional area decreases, the resistance increases, and thecurrent carrying capacity of open conductive pattern 103 decreases. So,the cross-sectional area of open conductive pattern 103 is selected toensure that open conductive pattern 103 is capable of carrying theanticipated operating current.

Open conductive pattern 103, as shown in FIG. 1A, is coupled to openconductive pattern 106 by conductive segment 112, which is perpendicularto open conductive pattern 103 and open conductive pattern 106, in oneembodiment. Conductive segment 112 is fabricated from a conductivematerial, such as gold, silver, copper, aluminum, aluminum-copper, or analloy of such a conductive material. Conductive segment 112 has across-sectional area. The cross-sectional area is selected to ensurethat conductive segment 112 has a current carrying capacity sufficientto carry the anticipated current in open stacked inductor 100.

Referring to FIG. 1C, open conductive pattern 106 is fabricated from aconductive material. In one embodiment, open conductive pattern 106 isfabricated from copper. In alternate embodiments, open conductor 106 isfabricated from gold, aluminum, silver, or an alloy of copper, gold,aluminum or silver. However, the fabrication of open conductor 106 isnot limited to a particular material. Any material that is capable ofconducting current is suitable for use in connection with the presentinvention. In addition, open conductive pattern 106 may be fabricatedfrom a different conductor than open conductive pattern 103 or openconductive pattern 109. For example, open conductive pattern 103 can befabricated from gold, while open conductive pattern 106 is fabricatedfrom copper.

Open conductive pattern 106 has a cross-sectional area. As thecross-sectional area decreases, the resistance increases, and thecurrent carrying capacity of open conductive pattern 106 decreases. So,the cross-sectional area of open conductive pattern conductor 106 isselected to ensure that open conductive pattern 106 is capable ofcarrying the anticipated operating current.

Open conductive pattern 106, as shown in FIG. 1C, is coupled to openconductive pattern 109 by conductive segment 115. Conductive segment 115is fabricated from a conductive material, such as gold, silver, copper,aluminum, aluminum-copper, or an alloy of such a conductive material.Conductive segment 115 has a cross-sectional area. The cross-sectionalarea is selected to ensure that conductive segment 115 has a currentcarrying capacity sufficient to carry the operating current in openstacked inductor 100.

Referring to FIG. 1D, open conductive pattern 109 is fabricated from aconductive material. In one embodiment, open conductive pattern 109 isfabricated from copper. In alternate embodiments, open conductivepattern 109 is fabricated from gold, aluminum, silver, or an alloy ofcopper, gold, aluminum or silver. However, the fabrication of openconductive pattern 109 is not limited to a particular material. Anymaterial that is capable of conducting current is suitable for use inconnection with the present invention.

Open conductive pattern 109 has a cross-sectional area. As thecross-sectional area decreases, the resistance increases, and thecurrent carrying capacity of open conductive pattern 109 decreases. So,the cross-sectional area of open conductor 109 is selected to ensurethat open conductive pattern 109 is capable of carrying the anticipatedoperating current.

As described briefly above, in a stacked open conductor inductor, eachopen conductive pattern can be fabricated from a different material. Forexample, open conductor pattern 103 can be fabricated from aluminum,open conductor pattern 106 can be fabricated from copper, and openconductor pattern 109 can be fabricated from gold. This provides aflexible environment for an inductor designer. In this environment, thedesigner can carefully control the heat generated by open patterninductor 100, shown in FIG. 1A, by incorporating higher conductivitymaterials into sections of the inductor. In addition, the designer cancontrol the location of a particular material in relation to thesubstrate. For example, copper, which may require a barrier layer toprotect a substrate from copper migration, can be located sufficientlyfar from the substrate so that a barrier layer is not required.

FIGS. 2A-2D illustrate the fabrication of integrated stacked openpattern inductor 200 on a substrate 203. Stacked open pattern inductor100 of FIG. 1A is included in stacked open pattern inductor 200.

FIG. 2A shows a side view of a cross-sectional slice of one embodimentof integrated stacked open pattern inductor 200. Inductor 200 comprisessubstrate 203, magnetic material layer 206, open inductor pattern 209,magnetic material 212, conductive segment 215, open inductor pattern218, magnetic material layer 221, conductive segment 224, open inductorpattern 227, and magnetic material layer 233. Open inductor pattern 209and open inductor pattern 218 have outside edges 231, and 232,respectively.

Magnetic material layer 206 is deposited on substrate 203, open inductorpattern 209 is deposited on magnetic material layer 206, magneticmaterial layer 212 is deposited above magnetic material layer 206, openinductor pattern 218 is deposited on magnetic material layer 212,magnetic material layer 221 is deposited above magnetic material layer212, open inductor pattern 227 is deposited on magnetic material layer221, and magnetic material layer 233 is deposited above magneticmaterial layer 221.

Substrate 203 is preferably a semiconductor, such as silicon.Alternatively, substrate 203 is gallium arsenide, germanium, or someother substrate material suitable for use in the manufacturing ofintegrated circuits.

Magnetic material layer 206 is deposited on the surface of substrate203. Magnetic material layers 212, 221, and 233 are deposited to fillthe interior area of open conductors 209, 218, and 227. Filling theinterior area of open conductors 209, 218, and 227 with a magneticmaterial increases the inductance of open pattern inductor 200. Theparticular type of the magnetic material selected for use in aparticular inductor design depends on the inductance requirement.

Magnetic material layer 206, in one embodiment, extends beyond outsideedge 231 of open conductive pattern 231. One advantage of extendingmagnetic material layer 206 beyond outside edge 231 of open conductivepattern 209 is that the magnetic flux generated by inductor 200 can beconfined to the area occupied by inductor 200. In an alternateembodiment, each magnetic material layer 212, 221, and 233 can beextended beyond outside edge 231 of open conductive pattern 209. Theamount of the extension is selected based on the anticipated current ininductor 200 and the magnetic permeability of magnetic material layers212, 221, and 233. In one embodiment, the extension is less than about amillimeter, and in other embodiments the extension is less than one-halfmillimeter or one-tenth millimeter.

FIGS. 2B-2D show a sequence of operations for forming part of inductor200 shown in FIG. 2A. Referring to FIG. 2B, open inductor pattern 209 isdeposited above magnetic material layer 206. The description of openinductor pattern 103 of FIG. 1A provided above also applies to openinductor pattern 209. Magnetic oxide layer 212 is deposited abovemagnetic material layer 206 and encapsulates open inductor pattern 209.

Referring to FIG. 2B, contact hole 236 is etched in magnetic oxide layer212 to expose open inductor pattern 209. Any etching process capable ofetching contact holes in magnetic oxide layer 212 is suitable for use inconnection with the present invention.

Referring to FIG. 2D, contact hole 236, shown in FIG. 2C, is filled witha conductive material to form conductive segment 215, which couples openinductor pattern 209 to open inductor pattern 218, shown in FIG. 2A.

The description of FIGS. 2B-2D provided above can be summarized. Theoperations include depositing an open inductor pattern 209, depositingan encapsulating magnetic oxide 212, etching a contact hole 236, anddepositing a conductive segment 215. Repeating the above describedoperations or a subset of the above described operations to create asandwich structure by stacking one or more open inductor patterns, oneor more layers of magnetic oxide, and one or more conductive segmentsabove open inductor pattern 209 increases the inductance of inductor200.

Referring to FIG. 3A, a side view of a cross-sectional slice of analternate embodiment of a rectangular open pattern inductor 300 isshown. Inductor 300 is formed on substrate 303 and comprises magneticmaterial layer 306, insulating layer 309, rectangular open inductorpattern 312, second insulating layer 315, second magnetic material layer318, and third insulating layer 321.

Magnetic material layer 306 is deposited on substrate 303, insulatinglayer 309 is deposited on magnetic material layer 306, rectangular openinductor pattern 312 is deposited on insulating layer 309, secondinsulating layer 315 is deposited on rectangular open inductor pattern312, and second magnetic material layer 318 is deposited on secondinsulating layer 315.

Substrate 303, in one embodiment, is a semiconductor. Silicon ispreferred, but the substrate 303 is not limited to a particular type ofmaterial. Germanium, gallium arsenide, and silicon-on-sapphire are allmaterials suitable for use as a substrate in the present invention.

Magnetic material layer 306, in one embodiment, is deposited on thesurface of substrate 303. The particular magnetic material selected foruse in a particular inductor design depends on the inductancerequirement. In one embodiment, in which a large inductance in a smallvolume is desired, a high permeability ferromagnetic material, such aspure iron or a NiFe alloy is selected. An example of a high permeabilityNiFe alloy is an alloy of 81% Ni and 19% Fe.

Insulating layer 309 is deposited on magnetic material layer 306. In oneembodiment, insulating layer 309 is an inorganic silicon oxide film. Inan alternate embodiment, insulating layer 309 is silicon dioxide. Instill another embodiment, which is perhaps preferable in a lowtemperature processing environment, insulating layer 309 is an organicinsulator, such as parylene and polyimide.

Rectangular open inductor pattern 312 is deposited on insulating layer309. In an alternate embodiment, open inductor pattern 312 is an opencircle. In a second alternate embodiment, inductor pattern 312 is a openpolygon, where the open polygon may be in the shape of a triangle,square, rectangle, octagon, or hexagon. A rectangular open inductorpattern, which is shown as inductor pattern 312 in FIG. 3A, ispreferred, since it is easy to manufacture. Inductor pattern 312 isfabricated from a high-conductivity material. In one embodiment, thehigh-conductivity material is gold. In an alternate embodiment, thehigh-conductivity material is copper.

Referring to FIG. 3A, second insulating layer 315 is deposited oninductor pattern 312, and is fabricated from the same materials asinsulating layer 309.

Second magnetic material layer 318 is deposited on second insulatinglayer 315, and is fabricated from the same materials as magneticmaterial layer 306. Second magnetic material layer 306 is preferablylocated above inductor pattern 312, and second magnetic material layer318 does not intersect the plane of magnetic material layer 306.

The contribution of the magnetic material layer 306 to the inductance ofinductor 300 can be precisely controlled during the manufacturingprocess. The thickness of the layer of magnetic material along with themagnetic properties of the material define the contribution of the layerto the inductance of the inductor. Once the properties of the materialare established during the preparation of the material, the thickness ofthe layer, which can be precisely controlled in an integrated circuitmanufacturing process, defines the contribution of the layer of magneticmaterial to the inductance.

Referring to FIG. 3B, three open inductor patterns are stacked to forminductor 330. Inductor 330 comprises base structure 333, sandwichstructure 336, second sandwich structure 339, third sandwich structure342, and conductive paths 345 and 347. Base structure 333 includessubstrate 350, magnetic material layer 353, and insulating layer 356.Sandwich structure 336 includes open inductor pattern 359, insulatinglayer 362, magnetic material layer 365, and insulating layer 368. Secondsandwich structure 339 is stacked on sandwich structure 336. Secondsandwich structure 339 includes open inductor pattern 371, insulatinglayer 374, magnetic material layer 377, and insulating layer 380. Thirdsandwich structure 342 includes open inductor pattern 383, insulatinglayer 386, magnetic material layer 389, and insulating layer 392.

Conductive path 347 couples sandwich structure 336 to second sandwichstructure 339, and serially connects open inductor pattern 359 toinductor pattern 371. A current flowing in the serially connectedinductor patterns creates a reinforcing magnetic field in magneticmaterial layer 365. Magnetic material layers 353 and 389 are locatedbelow inductor pattern 359 and above inductor pattern 383, respectively.Magnetic material layers 353 and 389 confine the magnetic flux and noiseradiated by a current flowing in inductor patterns 359, 368, and 383 tothe area bounded by the outer surfaces of magnetic material layers 353and 389. By stacking sandwich structures, in one embodiment, a largeinductance can be created without increasing the surface area on asubstrate occupied by the inductor.

The inductor of the present invention can be connected to otherelectronic devices in an integrated circuit. The inductor of the presentinvention is compatible with conventional silicon manufacturingprocesses, and structures for coupling passive devices, such asinductors, to other integrated circuit devices are known in the art.

Referring to FIG. 4, a diagram showing the currents and the resultingreinforcing magnetic fields of the three open inductor sandwich of FIG.3B is shown. Current 405 flows in stacked inductor 410. The resultingmagnetic field lines 415 are shown as confined by magnetic materialbarrier layers 420 and 425.

Referring to FIG. 5, a block diagram of a system level embodiment of thepresent invention is shown. System 500 comprises processor 505 includinga motherboard and memory device 510, which includes memory cells andcircuits including inductors of one or more of the types described abovein conjunction with FIGS. 1-4. Memory device 510 comprises memory array515, address circuitry 520, and read circuitry 530, and is coupled toprocessor 505 by address bus 535, data bus 540, and control bus 545.Memory device 510 is typically mounted on a motherboard. Processor 505,through address bus 535, data bus 540, and control bus 545 communicateswith memory device 510. In a read operation initiated by processor 505,address information, data information, and control information areprovided to memory device 510 through busses 535, 540, and 545. Thisinformation is decoded by addressing circuitry 520, including a rowdecoder and a column decoder, and read circuitry 530. Successfulcompletion of the read operation results in information from memoryarray 515 being communicated to processor 505 over data bus 540.

CONCLUSION

Various embodiments solve many of the problems listed above and otherswhich will become known to those skilled in the art upon reading andunderstanding the present disclosure. Some embodiments include a stackedopen pattern inductor fabricated above a semiconductor substrate. Thestacked open pattern inductor includes a plurality of parallel openconductive patterns embedded in a magnetic oxide or an insulator and amagnetic material. Embedding the stacked open pattern inductor in amagnetic oxide or in an insulator and a magnetic material increases theinductance of the inductor and allows the magnetic flux to be confinedto the area of the inductor. A layer of magnetic material may be locatedabove the inductor and below the inductor to confine electronic noisegenerated in the stacked open pattern inductor to the area occupied bythe inductor. The stacked open pattern inductor may be fabricated usingconventional integrated circuit manufacturing processes, and theinductor may be used in connection with computer systems.

Several embodiments of an inductor and a method for fabricatinginductors in an integrated circuit have been described. Theseembodiments are compatible with standard integrated circuitmanufacturing processes, and provide flexibility in the selection ofconductors and magnetic materials used in the construction of aninductor. Although specific embodiments have been illustrated anddescribed herein, it will be appreciated by those of ordinary skill inthe art that any arrangement which is calculated to achieve the samepurpose may be substituted for the specific embodiment shown. Thisapplication is intended to cover any adaptations or variations of thepresent invention. Therefore, it is manifestly intended that thisinvention be limited only by the claims and the equivalents thereof.

1. An inductor comprising: a first conductive pattern arranged in astack with a second conductive pattern and a third conductive pattern,wherein the first conductive pattern includes a material different froma material of at least one of the second conductive pattern or the thirdconductive pattern; a first conductive segment located between andcoupled to the first and second conductive patterns; a second conductivesegment located between and coupled to the second and third conductivepatterns, wherein the first and second conductive segments are onlyconductive segments in the entire inductor; and a substrate and amagnetic material overlying the substrate, wherein the first conductivepattern directly contacts the magnetic material, and the magneticmaterial directly contacts the substrate.
 2. The inductor of claim 1,wherein the second conductive pattern includes a first end and a secondend, the first conductive segment is coupled to the first end and to anend of the first conductive pattern, and the second conductive segmentis coupled to the second end and to an end of the third conductivepattern.
 3. The inductor of claim 1 further comprising a first magneticmaterial between the first and second conductive patterns.
 4. Theinductor of claim 3 further comprising a second magnetic materialbetween the second and third conductive patterns.
 5. The inductor ofclaim 4 further comprising a first insulator between the firstconductive pattern and the first magnetic material.
 6. The inductor ofclaim 5 further comprising a second insulator between the secondconductive pattern and the second magnetic material.
 7. The inductor ofclaim 4 further comprising a first insulator and a second insulatorbetween the first and second conductive patterns and sandwiching thefirst magnetic material.
 8. The inductor of claim 7 further comprising athird insulator and a fourth insulator between the second and thirdconductive patterns and sandwiching the second magnetic material.
 9. Theinductor of claim 8, wherein the second conductive pattern is embeddedin the second and third insulators.
 10. An inductor comprising: a firstconductive pattern overlying a second conductive pattern; a thirdconductive pattern overlying the second conductive pattern, wherein thefirst conductive pattern includes a material different from a materialof at least one of the second conductive pattern or the third conductivepattern; a first conductive segment coupled to the first conductivepattern and the second conductive pattern; a second conductive segmentcoupled to the second conductive pattern and the third conductivepattern; and a substrate and a magnetic material overlying thesubstrate, wherein the first conductive pattern directly contacts themagnetic material, and the magnetic material directly contacts thesubstrate.
 11. The inductor of claim 10, wherein the material of atleast one of the first conductive pattern, the second conductivepattern, or the third conductive pattern includes gold, silver, copper,aluminum, or an alloy of gold, silver, copper, or aluminum.
 12. Theinductor of claim 10, wherein the material of at least one of the firstconductive segment or the second conductive segment includes gold,silver, copper, aluminum, or an alloy of gold, silver, copper, oraluminum.
 13. The inductor of claim 10, wherein the material of thefirst conductive pattern includes copper.
 14. The inductor of claim 13,wherein the material of the second conductive pattern includes gold.